Field of the Invention
The invention concerns a liquid crystal display as is known for example from Japanese Patent Application JP 10-153764 A. There, the liquid crystal cell is integrated into a H-shaped structure, the crossbar of which makes up the optically active cell and the limbs of which act as spacers between a glass plate which is disposed thereover at the viewing side and a circuit carrier which is disposed therebeneath. Disposed beneath the optically active liquid crystal cell is a light guide that is surrounded by a reflecting housing and into which the light of a light emitting diode is laterally irradiated.
Rubber contacts for the electrical connection of the liquid crystal cell to the circuit carrier are disposed outside the limbs, between the overhanging glass plate and the circuit carrier. The mechanical structure is completed by a box-shaped frame which is fitted over the sandwich structure formed of the circuit carrier, the light guide, the liquid crystal cell and the glass plate and which, at the end edges of its side walls, is provided with L-shaped hooks which engage behind the edge of the circuit carrier. In that configuration, the module height of that liquid crystal display is determined by the thickness of the viewing window in the frame, the circuit carrier, the H-shaped structure and the glass plate which is pressed on to the H-shaped structure by the frame. It will be noted however that this is critical in regard to production engineering because local load peaks can result in damage to the glass plate and thus can result in the optical effect of that liquid crystal display being adversely impaired.
German Patent DE 35 26 511 C2, corresponding to U.S. Pat. No. 4,914,553, also discloses a liquid crystal cell backed by a light-guide panel. Light is irradiated from one of the narrow sides of the panel into the light-guide panel there substantially parallel to the main plane thereof. The light-guide panel which is wedge-shaped in the light irradiation direction and thus in longitudinal section is of a stepped configuration at its rear side which is remote from the liquid crystal cell, so that light is coupled out, at the step edges, through the thickness of the panel, into the liquid crystal display, in opposite relationship to the viewing or observation direction thereof. As a consequence of the discrete step geometry at the rear side of the light-guide plate however, in spite of the wedge shape thereof, it is not possible to reckon on light shining through the transmissive liquid crystal cell in a sufficiently homogeneous condition, and the sudden changes in brightness which occur between the steps in the light-guide panel in addition also make it difficult to read off an alphanumeric representation of information. That prior publication also does not specify how a compact modular structure that is also production-friendly in regard to inevitable component tolerances could be specifically configured for the display with the inclusion of the actuating circuit for its liquid crystal cell.
A liquid crystal display is also known from Japanese Patent JP 06-011718, in which a frame engages over a liquid crystal cell and the frame is secured to a flat light source.
U.S. Pat. No. 4,796,977 describes a liquid crystal display having a holding frame that is fixed to a holding plate by barb hooks which engage through openings in the holding plate.
The article ‘LED steht Kopf’ by Patrick Trueson from Design & Elektronik June 2002, pages 25 through 27, describes what is known as Reverse-Mount-LED Technology, in accordance with which a light emitting diode mounted on the rear side of a circuit board irradiates light through an opening in the circuit board into a light guide disposed on the front side of the circuit board and a liquid crystal cell disposed on the light guide. However, the light irradiation effect which takes place directly in opposite relationship to the viewing direction of the display causes very non-uniform illumination of the display area of the liquid crystal display as a great amount of light is radiated into the liquid crystal cell in the region of the opening in the circuit board, but the back-lighting becomes progressively darker, the further the display area to be illuminated is remote from that opening.